Alloy powder for flame spraying



3,341,337 ALLOY POWDER FOR FLAME SPRAYING Joseph F. Quaas, Island Park, and John P. Broderick, Bayside, N.Y., assignors to Eutectic Welding Alloys Corporation, Flushing, N.Y., a corporation of New York No Drawing. Filed Jan. 9, 1964, Ser. No. 336,628 12 Claims. (Cl. 106-1) This application is a continuation-in-part of application Ser. No. 289,474 filed June 21, 1963, now Patent No. 3,228,610.

This invention relates to nickel-iron-cobalt family base powdered mesh alloys for flame spraying, and it more particularly relates to such alloys containing boric acid.

Heretofore, elemental boron has been incorporated in nickel-iron-cobalt family base alloys employed for flame spraying because it helps flux and protect the powder during deposition and also lowers its melting point. However such use of elemental boron is likely to cause excessive boron pickup in the ultimate deposit which may make it too brittle.

An object of this invention is to provide self-fluxing nickel-iron-cobalt family base powdered mesh alloys for flame spraying that dependably deposit ductile coatings.

Another object is to provide such alloy powders that flow freely through a flame spraying torch.

In accordance with this invention a minor amount ranging from approximately 0.5 to 5.0% of boric acid powder of less than 325 mesh particle size is intermixed within a nickel-iron-cobalt family base alloy powder.

By the term nickel-iron-cobalt family base alloy is meant the metals of .Group VIII (IV) of the Periodic Arrangment of Elements.

The term boric acid as used herein, is meant to include acid-forming boron oxides, such as anhydrous boron trioxide (B as well as its hydrates such as orthoboric (H BO metaboric (HBO and tetraboric (H B -O acids. As a practical matter, the more stable orthoboric acid and the anhydride (B 0 are the most applicable constituents.

Generally speaking, the incorporation of non-metallic constituents is avoided in the flame spraying of alloy mesh since contamination of the alloy results. Since there is a wide difference in the specific gravities of the alloy mesh and such non-metallic constituents, they are normally excluded in alloy mesh used for flame spraying. Additionally, non-metallic fluxing materials are prone to pick up moisture during storage. The incorporation of non-metallic fluxes furthermore would be-thought to result in difiiculties in feeding the resulting mixtures through the mixing chamber and the orifice in the tip of the torch. It has been found, however,

the above disadvantages. Boric acid in the recited particle size doesn'ot show susceptibility to moisture pick up. The boric acid in the recited particle size actually lubricates and facilitates the flow of the alloy powder rather than obstructing it. The boric acid constituent also provides remarkably effective fluxing action because of its ability to form boron oxide in the heat of deposition. Boron oxide enhances the self-fluxing properties of the alloy powder and also the flow-ability of the deposited nickel alloy. These properties are far more effectively provided by the boric acid constituent than the previously used elemental boron without the same danger of excessive boron pickup in the ultimate deposit and its resultant embrittlement. A particularly eflective range of incorporation of the boric acid constitucut is from 13% by weight of the overall alloy.

The boric acid may be added to any conventional nickel-iron-cobalt family base alloy powder. Usually the alloy powder will be of relatively small particle size such hired States Patent Y as below, for example, 150 mesh. Generally speaking, the finer the particle size distribution of the alloy mesh, the

Suitable examples of nickel-iron-cobalt family base alloy powders are those containing in addition to the base metal small amounts of such ingredients as chromium, tungsten, carbon or phosphorous alone or in combination. The alloy may additionally contain small amounts of the nickel-iron-cobalt family metals different from the metal constituting the base metal. The alloy may further contain elemental boron as well as be free of elemental boron. The boric acid constituent is blended with the alloy mesh by any convenient method such as ball milling or in a twin-cone blender.

An illustrative example of nickel-iron-cobalt family base alloy with which the boric acid constiutent is effectively employed is one having a nickel base with a nickel content ranging from 88 to 90% by Weight and a phosphorous content ranging from 10 to 12% by Weight. The boric acid constituent is added in an amount of from 0.5 to 5.0% of the total composition or more effectively from 13% by weight thereof. Another and particularly effective example of a suitable nickel base alloy incorporates 90% nickel and 10% by weight of phosphorous. To this alloy is added boric acid to produce a finished composition of 98 percent nickel base alloy and 2 percent boric acid. The boric acid may be of any of the aforementioned types of boric acid-forming oxides previously mentioned and is generally described in the commercially available form as impalpable boric acid which is generally provided in the more stable orthoboric acid and its anhydride B 0 form. The above illustrated nickel base alloy may be converted to an iron or cobalt base alloy by substituting like amounts of these metals for the nickel.

Another example of this invention incorporates the following constituents in the alloy mesh powder in the indicated ranges and particular example of percent by weight:

EXAMPLE I Percent by weight Constituents on Boron Nickel, iron or cobalt With this example the aforementioned ranges of boric acid addition apply and particularly 1.5% by weight addition of boric acid together with 98.5% of the above alloy mesh.

EXAMPLE II Percent by Weight Constituents Range Example The aforementioned ranges of boric acid constituent apply for combination with the base alloy of this example, and a particularly effective combination is provided by utilizing 2.5% by weight of boric acid with 97.5% of the above alloy.

The employment of the boric acid constituent in the fine size less than 325 mesh when used in combination with a nickel-iron-cobalt family base alloy mesh which passes through a 150 mesh screen causes the boric acid powder to be virtually held in suspension even though the overall mix is heterogenous. The boric acid constituent therefore unexpectedly does not settle out during storage as might be expected from the difference in specific gravities in the mixture. The tendency of the boric acid constituent to pick up moisture is also unexpectedly negligible, and the fineness of the boric acid constituent and its inherent lubricating characteristics remarkably facilitates the flow of the powder through the relatively small orifices in a flame spraying torch.

During deposition the boric acid constituent provides unexpectedly voluminous and effective amounts of boron oxide which blankets the powder in the heat of deposition and prevents it from oxidizing. This oxide also lowers the melting point of the powder and improves its wettability and the flow of the deposited alloy, which greatly facilitates the application of ductile tenacious metal coatings upon metal surfaces. The employment of boric acid in a nickel-iron-cobalt family base alloy for flame spraying therefore unexpectedly proves to have none of the disadvantages that one might have associated with it and provides a remarkably efficient alloy mesh for use in flame spraying. This powdered alloy accordingly flows with remarkable freedom through the restricted orifices of a flame spraying torch, has remarkably effective fluxing action when it is being deposited and improves the physical characteristics of the deposited alloy. Also, the tendency of any excess of fine boric acid to float up and out of the deposited alloy prevents contamination and embrittlement of the deposited coating.

The alloy powders of the present invention containing boric acid may be used alone during flam spraying or they may be mixed with other materials, either pre-mixed and sprayed or separately, but simultaneously, sprayed. Thus, for example, when the base alloys in mesh form are used as a matrix alloy for tungsten carbide and wherein the carbide and matrix alloy are sprayed together or simultaneously, additions of boric acid are of importance for the same reasons as previously mentioned. The requirement for fluxing becomes more acute since the matrix alloy usually represents to 50 percent by weight of the overall material being deposited. Therefore, even though the matrix alloy may contain some additional fluxing agents, there are not enough self-fluxing elements present for suflicient reduction and wettability. The addition of boric acid therefore serves to supply the self-fluxing elements.

Generally speaking, alloys of the above type comprise from 50 to 80 and preferably 60 percent by weight of tungsten carbide particles and from 20 to 50 and preferably percent by weight of the matrix alloy including the boric acid. The tungsten carbide particles may be of the cast or sintered type but it is preferred to use cast particles. Suitable matrix alloys may be illustrated by the above mentioned formulations. Further examples particularly useful as matrix alloys, but also useful for flame spraying in general include the following:

EXAMPLE III EXAMPLE IV Range in Example in Constituent percent percent by weight by weight Nickel 1. 05. 0 3.0 Chromium 26. 0-32. 0 28. 0 0.5-3.0 1.0 0. 55. 0 2. 0 0. 8-2. 0 l. 0 3. 5-7. 5 4. 5 Molybdenum 0. 05. 0 3. 0 Nickel, iron or cobalt Balance Balance It is of course understood that the nickel-iron-cobalt family base alloy powders illustrated above are merely exemplary of powders useful for flame spraying which may be unexpectedly improved by the incorporation of boric acid. The formulations of Examples I to II may be used as the matrix alloys when combined with tungsten carbide and the formulations of Examples III and IV may be used alone for flame spraying.

What is claimed is:

1. A powdered mesh composition for flame spraying consisting essentially of a major proportion of an alloy having as its base a member selected from the group consisting of nickel, iron and cobalt and from 0.5 to 5.0 percent by total composition weight of boric acid powder, said powder having a particle size of less than 325 mesh whereby said composition is protected from oxidation during deposition and its flow is facilitated.

2. The powdered mesh composition of claim 1 wherein the base alloy is a nickel alloy.

3. The powdered mesh composition of claim 1 wherein the base alloy is an iron alloy.

4. The powdered mesh composition of claim 1 wherein the base alloy is a cobalt alloy.

5. The powdered mesh composition of claim 1 wherein the boric acid is present in an amount of from 1.0 to 3.0 percent by total composition weight.

6. The powdered mesh composition of claim 1 wherein the alloy consists essentially of the following ingredients in the following percentages by weight of total alloy:

Constituents: Percent by weight Phosphorous 10-12 A member selected from the group consisting of the nickel, iron and cobalt 88-90 7. The powder mesh composition of claim 6 wherein the alloy is a nickel base alloy.

8. The powdered mesh composition of claim 1 wherein the alloy consists essentially of the following ingredients in the following percentages by weight of total alloy:

Constituents: Range in percent by weight Carbon .01 to 1.00

. Chromium 1.00 to 20.00 Silicon 1.00 to 5.00 Iron .01 to 5.00 Boron c- 1.00 to 5.00

A member selected from the group consisting of nickel, iron and cobalt 97.98 to 64.00

9. The powdered mesh composition of claim 1 wherein the alloy consists essentially of the following ingredients in the following percentages by weight of total alloy:

A member selected from the group consisting of nickel, iron and cobalt 86.80 to 98.64

10. A tungsten carbide laden composition comprising from 50-80 percent by weight tungsten carbide and from 20 to 50 percent by weight of a mixture, said mixture consisting essentially of a major proportion of an alloy having as its base a member selected from the group consisting of nickel, iron and cobalt and from 0.5 to 5.0 percent by weight of boric acid powder, said powder having a particle size of less than 325 mesh whereby said tungsten carbide laden alloy is protected from oxidation during deposition and its flow is facilitated,

11. The tungsten carbide laden composition of claim 10 wherein the alloy consists essentially of the following ingredients in the following percentages by weight of total alloy:

Constituent: Range in percent by weight Silicon -u 1.5-5.0 Boric acid 0.5-5.0 Chromium 0-20 Molybdenum 0-7 A member selected from the group consisting of nickel, iron and cobalt Balance '12. The tungsten carbide laden composition of claim 10 wherein the alloy consists essentially of the following ingredients in the following percentages by weight of total alloy:

Constituent: Range in percent by weight Nickel 1.0-5.0 Chromium 26.0-32.0 Silicon 0.5-3.0 Boric acid 0.5-5.0 Carbon 0.8-2.0 Tungsten 3.5-7.5 Molybdenum 0.0-5.0 A member selected from the group consisting of nickel, iron and cobalt Balance References Cited UNITED STATES PATENTS 3,025,182 3/1962 'Schrewelius 117-131 XR 3,035,934 5/1962 Cape 117-22 L. B. HAYES, Assistant Examiner. 

1. A POWDERED MESH COMPOSITION FOR FLAME SPRAYING CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF AN ALLOY HAVING AS ITS BASE A MEMBER SELECTED FROM THE GROUP CONSISTING OF NICKEL, IRON AND COBALT AND FROM 0.5 TO 5.0 PERCENT BY TOTAL COMPOSITION WEIGHT OF BORIC ACID POWDER, SAID POWDER HAVING A PARTICLE SIZE OF LESS THAN 325 MESH WHEREBY SAID COMPOSITION IS PROTECTED FROM OXIDATION DURING DEPOSITION AND ITS FLOW IS FACILITATED.
 10. A TUNGSTEN CARBIDE LADEN COMPOSITION COMPRISING FROM 50-80 PERCENT BY WEIGHT TUNGSTEN CARBIDE AND FROM 20 TO 50 PERCENT BY WEIGHT OF A MIXTURE, SAID MIXTURE CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF AN ALLOY HAVING AS ITS BASE A MEMBER SELECTED FROM THE GROUP CONSISTING OF NICKEL, IRON AND COBALT AND FROM 0.5 TO 5.0 PERCENT BY WEIGHT OF BORIC ACIE POWDER, SAID POWDER HAVING A PARTICLE SIZE OF LESS THAN 325 MESH WHEREBY SAID TUNGSTEN CARBIDE LADEN ALLOY IS PROTECTED FROM OXIDATION DURING DEPOSITION AND ITS FLOW IS FACILITATED. 